Process for collection of continuous fibers as a uniform batt

Abstract

A process and apparatus for collecting continuous fibers or filaments as a uniform batt comprises a filament emitter in the form of a spinning die, a venturi, a diffuser, and a fiber collection bed. The filaments move downward after being created by the emitter, and exhaust ports create in the diffuser an airflow having a direction against the flow of the filaments so that the filaments are decelerated before contacting the fiber collection bed.

1. A process for preparing a fiber batt from blow spun fibers comprising:
 a) heating a spinnable substance to a temperature sufficient to allow the spinnable substance to flow; 
 b) forming at least one fiber by passing the spinnable substance into a spinning apparatus and through at least one capillary located within the spinning apparatus, wherein said at least one fiber has an initial velocity; 
 c) contacting said at least one fiber with at least one flowing stream of gas; 
 d) contacting said at least one fiber with at least one additional flowing stream of gas to place said fiber under tension, wherein the velocity of said at least one additional flowing stream of gas is greater than said initial velocity of the at least one fiber; 
 e) passing said at least one fiber and said additional flowing stream of gas into a venturi; 
 f) thereafter passing said at least one fiber into a diffuser, comprising an upper portion and a lower portion, wherein the diffuser is shaped so that its walls curve outwards to provide for a horizontal component and an upward vertical component to the gas flow thereby dissipating the at least one additional flowing stream of gas to reduce the velocity of the at least one additional flowing stream of gas thereby reducing the velocity of the at least one fiber to a final velocity; 
 g) passing said at least one fiber out of said diffuser at said final velocity; and, 
 h) collecting said at least one fiber to form a fiber batt. 
 
     
     
       2. The process of  claim 1 , further comprising controlling the rate of dissipating said at least one additional stream of gas, by provision of exhaust ports located within the diffuser, wherein the exhaust ports are positioned to draw gas from the lower portion of the diffuser and so provide upward and horizontal components to an exhaust gas stream thereby controlling the final velocity of the at least one fiber. 
     
     
       3. The process of  claim 2  wherein the rate of dissipation of said at least one additional stream of gas is increased to effectuate an increase in the volumetric density of the fiber batt. 
     
     
       4. The process of  claim 2  wherein said initial velocity of the at least one fiber as it exits said spinning apparatus is reduced to said final velocity when it exits the diffuser and wherein the ratio of said initial velocity to said final velocity is up to 50:1. 
     
     
       5. The process of  claim 1 , wherein said at least one fiber is spun from a carbonaceous pitch. 
     
     
       6. The process of  claim 1 , wherein said at least one fiber is spun from a solvated mesophase pitch. 
     
     
       7. The process of  claim 1 , further comprising controlling the velocity of said at least one fiber in the diffuser by provision of exhaust ports located within said diffuser positioned to draw gas from the lower portion of the diffuser and so provide upward and horizontal components to an exhaust gas stream thereby controlling the final velocity of the at least one fiber. 
     
     
       8. The process of  claim 7  wherein control of the final velocity of said at least one fiber is affected by control of the amounts of gas exhausted through said exhaust, the amount of gas exhausted through a collection plate and the amount of additional gas fed into the venturi. 
     
     
       9. The process of  claim 8  wherein said initial velocity of the at least one fiber as it exits said spinning apparatus is reduced to said final velocity when it exits the diffuser and wherein the ratio of said initial velocity to said final velocity is up to 50:1. 
     
     
       10. The process of  claim 7 , wherein the exhaust ports comprise one or more openings in the opposing walls of the lower portion of the diffuser. 
     
     
       11. The process of  claim 10 , wherein the exhaust ports comprise perforated plates. 
     
     
       12. The process of  claim 1 , wherein the venturi and the diffuser have opposing walls centered about an axis drawn vertically through the center of the venturi. 
     
     
       13. The process of  claim 12 , wherein the distance between the axis and the opposing walls of a second open end of the venturi is greater than the distance between the axis and the opposing walls of a first open end of the venturi. 
     
     
       14. The process of  claim 12 , wherein the distance between the axis and the opposing walls of a second open end of the diffuser is greater than the distance between the axis and the opposing walls of a first open end of the diffuser. 
     
     
       15. The process of  claim 12 , wherein at least a portion of the opposing walls of the upper portion of the diffuser curve in an outward direction relative to the axis. 
     
     
       16. The process of  claim 12 , wherein at least a portion of the opposing walls of the lower portion of the diffuser curve in an outward direction relative to the axis. 
     
     
       17. The process of  claim 2 , wherein the exhaust ports comprise one or more openings in the opposing walls of the lower portion of the diffuser. 
     
     
       18. The process of  claim 17 , wherein the exhaust ports comprise perforated plates. 
     
     
       19. The process of  claim 1 , wherein the fibers are collected on a collecting surface. 
     
     
       20. The process of  claim 19 , further comprising exhausting air beneath the collecting surface. 
     
     
       21. The process of  claim 1 , wherein the venturi and the diffuser are contiguous. 
     
     
       22. The process of  claim 1 , wherein the distance between the second opening of the capillary and the first open end of the venturi is from about 0.25 inches (0.635 cm) to about 100 inches (254 cm). 
     
     
       23. The process of  claim 22 , wherein the distance between the second opening of the at least one capillary and the first open end of the venturi is from about 2 inches (5.08 cm) to about 4 inches (10.16 cm).